1. Field of the Invention
This invention relates to shell and tube heat exchangers and in particular to such heat exchangers having a pull-through removable tube bundle.
2. Prior Art
Shell and tube type heat exchangers of various designs are widely used in industry, especially in the chemical process industry. Design details of this type of heat exchanger are extensively described in publications of the Tubular Exchanger Manufacturers Association (TEMA) and in various other engineering publications. A detailed description of TEMA-style shell and tube heat exchangers, including multi-pass tube side heat exchangers as well as other heat exchangers is set forth in Perry's Chemical Engineers' Handbook, 7.sup.th ed., McGraw-Hill. A number of the designs set forth in these as well as other publications and patents are directed to methods and apparatus for holding and maintaining tubes and tube bundles, especially for ease of removal for maintenance purposes.
U.S. Pat. No. 3,231,012 to Norris discloses a method and apparatus for replacing a seal in an expandable shell double bonnet heat exchanger.
U.S. Pat. No. 3,380,516 to Kaye describes a method and apparatus for providing an expansion joint at the end of each tube in a tube type heat exchanger.
U.S. Pat. No. 3,398,787 to Bevevino discloses the use of an expansion joint to compensate for the movement of the tubesheet as the tubes expand and contract.
U.S. Pat. No. 4,164,255 to Binet et al. discloses a shell and tube heat exchanger wherein an array of tubes is held at each end in a perforated end plate having a flanged support sleeve in each tube hole with the flanges bolted to the outer face of the perforated end plate.
U.S. Pat. No. 4,627,486 to Baron discloses a tube-type heat exchanger wherein the ends of the tubes are held in a tubesheet, extending slightly beyond the outer face of the tubesheet. A retaining plate bolted to the outside of the tubesheet having holes in alignment with each tube end, each hole being large enough to fit over the extended end of the tube.
U.S. Pat. No. 4,635,712 to Baker et al. discloses a high pressure shell and tube heat exchanger utilizing dual tube sheet assemblies, each including an inner tubesheet and an outer tubesheet separated by spacers.
Various multi-pass shell and tube heat exchangers have been designed to improve heat transfer performance by routing the tubeside fluid first through one tube or set of tubes and then reversing the direction of flow by routing the fluid through another tube or set of tubes in the opposite direction. This arrangement requires the use of one or more pass partitions at one or both ends of the exchanger depending on the number of passes required. Typically, in a shell and tube heat exchanger, the tubes are the components most likely to corrode and thus, are the components most likely to require maintenance and/or replacement. For this purpose, and for ease of cleaning, removable bundles are advantageous. However, heat exchangers with more than two passes on the tubeside and with a removable bundle require expensive and awkward designs. Typically these include a return and pass-partitioned inner tubeside bonnet bolted directly to the rear tube sheet in order to seal the bonnet pass-partitions against the tube sheet as the tube bundle expands and contracts, enclosed within the shell. The shell, in turn, must have a shell closure or bonnet. The inner tube side chamber (channel or bonnet) requires a flange which is sealed and bolted to the tubesheet. The portion of the tubesheet that is used for the attachment of the flange is then unavailable for holding the ends of tubes. As a result, the available tube space within the shell is greatly diminished.
It is an object of the present invention to provide an improved shell and tube multi-pass tubeside heat exchanger having a compact design.
It is a further object to provide a multi-pass tubeside heat exchanger having a readily removable tube bundle.
It is a still further object to provide a shell and tube multi-pass heat exchanger of compact design, having more than two passes on the tube side and having a removable bundle.